Fixed javadocs for skipStochasticTests

Fixes #278.

Clarified what the stochastic tests are, and what the flag to skip them
is provided for.

Author: jroper

Diff for: tck/src/main/java/org/reactivestreams/tck/IdentityProcessorVerification.java

@@ -172,7 +172,15 @@ public long boundedDepthOfOnNextAndRequestRecursion() {
 
   /**
    * Override and return {@code true} in order to skip executing tests marked as {@code Stochastic}.
-   * Such tests MAY sometimes fail even though the impl
+   * <p>
+   * Such tests MAY sometimes pass even when the implementation doesn't implement the requirement correctly. These
+   * tests are typically testing things that can't be proven by a test, for example, testing for concurrency issues
+   * like ensuring that two methods are not invoked concurrently. In such cases, the implementation may pass the test
+   * out of luck.
+   * <p>
+   * This flag is provided because for some implementations, the stochastic tests can be expensive to run, and given
+   * that they emit false positives and so don't actually mean anything, the value from running them may not justify
+   * the cost.
    */
   public boolean skipStochasticTests() {
     return false;